The main objective with this project is to learn more about the role of genetic and environmental factors in the development of the central nervous system. The visual pathway of the cat and the macaque has been selected because of the investigator's familiarity with its normal morphology and physiology. Our studies in the cat have shown that neural connections including those in the visual cortex are innately determined but require normal visual stimulation for their maintenance during a critical period shortly after birth. Similar behavioral and physiological studies of development of the visual system will be carried out in the Macaque with the specific purpose of learning about the neural mechanisms behind conditions such as strabismic amblyopia, alternation and visual defects following congenital cataracts. A special effort will be made to study the morphological changes caused by visual deprivation using both classical neuroanatomical methods and electron microscopy. Finally, a congenital abnormality of the optic nerve decussation observed in the Siamese cat will be studied using physiological, anatomical and genetic tools.